1. Field of the Disclosure
The present disclosure relates to an inverter for supplying a load-adaptive boost voltage, and particularly, to an inverter capable of automatically adjusting an output voltage when an inverter is driven according to an amount of load and a load state to prevent failure and an accident that may occur due to an overcurrent at an initial stage of driving.
2. Background of the Disclosure
An inverter is a unit for switching received direct current (DC) power into alternating current (AC) power by a switching element and supplying the AC power to an induction motor to drive the induction motor.
The inverter generates a pulse width modulation (PWM) signal to control a switching element by the PWM signal to generate AC power, and vary a voltage and a frequency of AC power by controlling a pulse width of the PWM signal, thereby freely converting torque and a rotation speed of the induction motor.
Meanwhile, the induction motor is a motor used in various fields from fans and pumps to hoist loads such as cranes and elevators.
FIG. 1 is a schematic view of a general inverter system.
An inverter 2 receives power from a 3-phase power source 1 and converts the received power into a predetermined voltage and frequency to drive an induction motor 3.
The inverter 2 may be a 2-level inverter or a multi-level inverter of 3 levels or greater.
In driving an elevator load using an inverter, in a case in which the inverter is controlled according to an open loop control method, an output voltage is insufficient at an initial stage of driving, so an overcurrent may flow to cause the inverter to have a fault, or an elevator may instantaneously slide to cause people in an elevator to feel insecure.
In order to present such a problem, a manual boost method has been proposed.
The manual boost method is a method of operation by providing a value set by a user as a boost value. As illustrated in FIG. 2, a boost voltage amount may be set to be in inverse proportion such that a large amount is boosted in a low speed region and a small amount is boosted in a high speed region.
However, according to the manual boost method, torque may be insufficient in a low speed region or torque excessive more than necessary may be applied according to an amount of user setting. Also, according to the manual boost method, since a boost voltage amount is applied regardless of a load amount, a case in which an output voltage is insufficient or an output voltage is excessive occurs according to a load amount.